Although dominant molecular subtypes can be distinguished in most cases in SCLC, there is often significant heterogeneity in pathology and phenotypic switching may occur.[81] It has been found that SCLC‐A subtype can be converted to SCLC‐N subtype and further to SCLC‐I subtype under MYC drive.[82, 83, 84] Single‐cell sequencing analysis shows that MUC1 expression is the most prominent in the SCLC‐A subtype and normal epithelial stromal cells (Figure 1E–G). Here, MYC is linked to small cell lung carcinoma.